N,N&#39;-di(phenylalky)-substituted perylene-based tetracarboxylic diimide compounds as n-type semiconductor materials for thin film transistors

ABSTRACT

A thin film transistor comprises a layer of organic semiconductor material comprising a tetracarboxylic diimide 3,4,9,10-perylene-based compound having, attached to each of the imide nitrogen atoms a substituted or unsubsitituted phenylalkyl group. Such transistors can further comprise spaced apart first and second contact means or electrodes in contact with said material. Further disclosed is a process for fabricating an organic thin-film transistor device, preferably by sublimation or solution-phase deposition onto a substrate, wherein the substrate temperature is no more than 100° C.

FIELD OF THE INVENTION

The present invention relates to the useN,N′-bis[phenylalkyl]perylene-3,4:9,10-bis(dicarboximide) compounds assemiconductor materials in n-channel semiconductor films for thin filmtransistors. The invention relates to the use of these materials in thinfilm transistors for electronic devices and methods of making suchtransistors and devices.

BACKGROUND OF THE INVENTION

Thin film transistors (TFTs) are widely used as a switching element inelectronics, for example, in active-matrix liquid-crystal displays,smart cards, and a variety of other electronic devices and componentsthereof. The thin film transistor (TFT) is an example of a field effecttransistor (FET). The best-known example of an FET is the MOSFET(Metal-Oxide-Semiconductor-FET), today's conventional switching elementfor high-speed applications. Presently, most thin film devices are madeusing amorphous silicon as the semiconductor. Amorphous silicon is aless expensive alternative to crystalline silicon. This fact isespecially important for reducing the cost of transistors in large-areaapplications. Application of amorphous silicon is limited to low speeddevices, however, since its maximum mobility (0.5-1.0 cm²/V sec) isabout a thousand times smaller than that of crystalline silicon.

Although amorphous silicon is less expensive than highly crystallinesilicon for use in TFTs, amorphous silicon still has its drawbacks. Thedeposition of amorphous silicon, during the manufacture of transistors,requires relatively costly processes, such as plasma enhanced chemicalvapor deposition and high temperatures (about 360° C.) to achieve theelectrical characteristics sufficient for display applications. Suchhigh processing temperatures disallow the use of substrates, fordeposition, made of certain plastics that might otherwise be desirablefor use in applications such as flexible displays.

In the past decade, organic materials have received attention as apotential alternative to inorganic materials such as amorphous siliconfor use in semiconductor channels of TFTs. Organic semiconductormaterials are simpler to process, especially those that are soluble inorganic solvents and, therefore, capable of being applied to large areasby far less expensive processes, such as spin-coating, dip-coating andmicrocontact printing. Furthermore organic materials may be deposited atlower temperatures, opening up a wider range of substrate materials,including plastics for flexible electronic devices. Accordingly, thinfilm transistors made of organic materials can be viewed as a potentialkey technology for plastic circuitry in display drivers, portablecomputers, pagers, memory elements in transaction cards, andidentification tags, where ease of fabrication, mechanical flexibility,and/or moderate operating temperatures are important considerations.

Organic materials for use as potential semiconductor channels in TFTsare disclosed, for example, in U.S. Pat. No. 5,347,144 to Garnier etal., entitled “Thin-Layer Field-Effect Transistors with MIS StructureWhose Insulator and Semiconductors Are Made of Organic Materials.”

Organic semiconductor materials that can be used in TFTs to provide theswitching and/or logic elements in electronic components, many of whichrequire significant mobilities, well above 0.01 cm²/Vs, and currenton/off ratios (hereinafter referred to as “on/off ratios”) greater than1000. Organic TFTs having such properties are capable of use forelectronic applications such as pixel drivers for displays andidentification tags. However, most of the compounds exhibiting thesedesirable properties are “p-type” or “p-channel,” meaning that negativegate voltages, relative to the source voltage, are applied to inducepositive charges (holes) in the channel region; of the device. N-typeorganic semiconductor materials can be used in TFTs as an alternative top-type organic semiconductor materials, where the terminology “n-type”or “n-channel” indicates that positive gate voltages, relative to thesource voltage, are applied to induce negative charges in the channelregion of the device.

Moreover, one important type of TFT circuit, known as a complementarycircuit, requires an n-type semiconductor material in addition to ap-type semiconductor material. See Dodabalapur et al. in “Complementarycircuits with organic transistors” Appl. Phys. Lett. 1996, 69, 4227. Inparticular, the fabrication of complementary circuits requires at leastone p-channel TFT and at least one n-channel TFT. Simple components suchas inverters have been realized using complementary circuitatchitecture. Advantages of complementary circuits, relative to ordinaryTFT circuits, include lower power dissipation, longer lifetime, andbetter tolerance of noise. In such complementary circuits, it is oftendesirable to have the mobility and the on/off ratio of an n-channeldevice to be similar in magnitude to the mobility and the on/off ratioof a p-channel device. Hybrid complementary circuits using an organicp-type semiconductor and an inorganic n-type semiconductor are known, asdescribed in Dodabalapur et al. (Appl. Phys. Lett. 1996, 68, 2264.), butfor ease of fabrication, an organic n-channel semiconductor materialwould be desired in such circuits.

Only a limited number of organic materials have been developed for useas a semiconductor n-channel in TFTs. One such materialbuckminsterfullerene C60 exhibits a mobility of 0.08 cm²/Vs but isconsidered to be unstable in air. See R. C. Haddon, A. S. Perel, R. C.Morris, T. T. M. Palstra, A. F. Hebard and R. M. Fleming, “C₆₀ Thin FilmTransistors” Appl. Phys. Let. 1995, 67, 121. Perfluorinated copperphthalocyanine has a mobility of 0.03 cm²/Vs, and is generally stable toair operation, but substrates must be heated to temperatures above 100°C. in order to maximize the mobility in this material. See “NewAir-Stable n-Channel Organic Thin Film Transistors” Z. Bao, A. J.Lovinger, and J. Brown J. Am. Chem, Soc. 1998, 120, 207. Other n-channelsemiconductors, including some based on a naphthalene framework, havealso been reported, but with lower mobilities. See Laquindanum et al.,“n-Channel Organic Transistor Materials Based on NaphthaleneFrameworks,” J. Am. Chem, Soc. 1996, 118, 11331. One suchnaphthalene-based n-channel semiconductor material,tetracyanonaphthoquino-dimethane (TCNNQD), is capable of operation inair, but the material has displayed a low on/off ratio and is alsodifficult to prepare and purify.

Aromatic tetracarboxylic diimides, based on a naphthalene aromaticframework, have also been demonstrated to provide, as an n-typesemiconductor, n-channel mobilities greater than 0.1 cm²/Vs usingtop-contact configured devices where the source and drain electrodes areon top of the semiconductor. Comparable results could be obtained withbottom contact devices, that is, where the source and drain electrodesare underneath the semiconductor, but a thiol underlayer needed to beapplied between the electrodes, which had to be gold, and thesemiconductor. See Katz et al. “Naphthalenetetracarboxylic Diimide-Basedn-Channel Transistor Semiconductors: Structural Variation andThiol-Enhanced Gold Contacts” J. Am. Chem. Soc. 2000 122, 7787; “ASoluble and Air-stable Organic Semiconductor with High ElectronMobility” Nature 2000 404, 478; Katz et al., European Patent ApplicationEP1041653 or U.S. Pat. No. 6,387,727. In the absence of the thiolunderlayer, the mobility was found to be orders of magnitude lower inbottom-contact devices. Relatively higher mobilities have been measuredin films of perylene tetracarboxylic diimides having linear alkyl sidechains using pulse-radiolysis time-resolved microwave conductivitymeasurements. See Struijk et al. “Liquid Crystalline Perylene Diimides:Architecture and Charge Carrier Mobilities” J. Am. Chem. Soc. Vol. 2000,122, 11057. However, initial devices based on materials having aperylene framework used as the organic semiconductor led to devices withlow mobilities, for example 10⁻⁵ cm²/Vs for perylene tetracarboxylicdianhydride (PTCDA) and 1.5×10⁻⁵ cm² /Vs for NN′-diphenyl perylenetetracarboxylic acid diimide (PTCDI-Ph. See Horowitz et al. in “Evidencefor n-Type Conduction in a Perylene Tetracarboxylic Diimide Derivative”Adv. Mater. 1996, 8, 242 and Ostrick, et al. J. Appl. Phys. 1997, 81,6804.

US Patent Pub. No. 2002/0164835 A1 to Dimitrakopoulos et al. disclosesimproved n-channel semiconductor films made of perylene tetracarboxylicacid diimide compounds, one example of which isN,N′-di(n-1H,1H-perfluorooctyl) perylene-3,4,9,10-tetracarboxylic aciddiimide. Substituents attached to the imide nitrogens in the diimidestructure comprise alkyl chains, electron deficient alkyl groups,electron deficient benzyl groups, the chains preferably having a lengthof four to eighteen atoms. U.S. Pat. No. 6,387,727 B1 to Katz et al.discloses fused-ring tetracarboxylic diimide compounds, one example ofwhich is N,N′-bis(4-trifluoromethylbenzyl)naphthalene-1,4,58,-tetracarboxylic acid diimide. Such compoundsare pigments that are easier to reduce.

There is a need in the art for new and improved organic semiconductormaterials for transistor materials and improved technology for theirmanufacture and use. There is especially a need for n-type semiconductormaterials exhibiting significant mobilities and current on/off ratios inorganic thin film transistor devices.

SUMMARY OF THE INVENTION

The present invention relates to the use, in n-channel semiconductorfilms for thin film transistors, N,N′-di(arylalkyl) perylenetetracarboxylic diimide compounds having, attached to each of the twoimide nitrogens, an arylalkyl group, wherein the aryl group, which maybe substituted or unsubstituted, is attached via a divalent hydrocarbonto each imide nitrogen. Such films are capable of exhibiting, in thefilm form, the highest reported field-effect electron mobility, greaterthan 0.7 cm²/Vs. Such semiconductor films are also capable of providingdevice on/off ratios in the range of at least 10⁵.

Another aspect of the present invention is the use of such n-channelsemiconductor films inorganic thin film transistors, each suchtransistors further comprising spaced apart first and second contactmeans connected to an n-channel semiconductor film. A third contactmeans can be spaced from said first and second contact means and that isadapted for controlling, by means of a voltage applied to the thirdcontact means, a current between the first and second contact meansthrough said film. The first, second, and third contact means cancorrespond to a drain, source, and gate electrode in a field effecttransistor.

Another aspect of the present invention is directed to a process forfabricating a thin film transistor, preferably by sublimation orsolution-phase deposition of the n-channel semiconductor film onto asubstrate, wherein the substrate temperature is at a temperature of nomore than 100° C. during the deposition.

More particularly, the present invention is directed to an articlecomprising, in a thin film transistor, a thin film of organicsemiconductor material that comprises an N,N′-di(arylalkyl)-substitutedperylene-based tetracarboxylic diimide compound having a substituted orunsubstituted carbocyclic aromatic ring system attached to each imidenitrogen atom through a divalent hydrocarbon group, wherein any optionalsubstituents on the aryl rings comprises at least one electron donatingorganic group, i.e., if one or more substituents are present on one orboth of the two carbocyclic ring systems, such substituents comprise atleast one electron donating group.

In one embodiment of the present invention,N,N′-di(arylalkyl)perylene-based tetracarboxylic diimide compounds arerepresented by the following structure:

wherein, X is a divalent —CH₂— group, n=1-3, and R1, R2, R3, R4, R5, R6,R7, R8, R9, and R10 are each independently H or an electron donatingorganic group. Preferably, R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10on the phenyl rings comprises at least one C1-C8 alkyl substituent.Preferred organic groups include, for example, CH₃, linear or branchedC2-C4 alkyl, C1-C8 alkylene (a monovalent unsaturated aliphatichydrocarbon), or C1-C8 alkoxy.

It is preferred that when n=1 at least two of R1, R2, R3, R4 and R5 areH and at least two of R6, R7, R8, R9, and R10 are H. When n=1, morepreferred structures are those in which at least three of R1, R2, R3, R4and R5 are H and at least three of R6, R7, R8, R9, and R10 are H. Whenn=1, still more preferred structures are those in which either all ofR1, R2, R3, R4, R5, R6, R8, R9, and R10 are H, and R7 is CH₃; or all ofR2, R3, R4, R5, R7, R8, R9, and R10 are H, and both R1 and R6 are CH₃.Preferably, if the divalent hydrocarbon in Structure I is a —CH₂— group,then at least one phenyl group is substituted with a C1 to C4 containingalkyl group.

It is preferred that when n=2 at least two of R1, R2, R3, R4 and R5 areH and at least two of R6, R7, R8, R9, and RIO are H. When n=2, morepreferred structures are those in which at least three of R1, R2, R3, R4and R5 are H and at least three of R6, R7, R8, R9, and R10 are H. Whenn=2, still more preferred structures are those in which either all ofR1, R2, R3, R4, R5, R6, R8, R9, and R10 are H, and R7 is CH₃; or all ofR2, R3, R4, R5, R7, R8, R9, and R10 are H, and both R1 and R6 are CH₃.When n=2, most preferred is that structure in which all of R1, R3, R4,R5, R6,R8, R9, and R10 are H, and both R2 and R7 are CH₃.

In the above Structure I, a first and second dicarboxylic imide moietyis attached on opposite sides of the perylene nucleus, at the 3,4 and9,10 positions of the perylene nucleus. The perylene nucleus can beoptionally substituted with up to eight independently selected Y groups,wherein m is any integer from 0 to 8.

Advantageously, an n-channel semiconductor film used in a transistordevice according to the present invention does not necessarily require,for obtaining high mobilities, prior treatment of the first and secondcontact means connected to the film. Furthermore, the compounds used inthe present invention possess significant volatility so that vapor phasedeposition, where desired, is available to apply the n-channelsemiconductor films to a substrate in an organic thin film transistor.

As used herein, “a” or “an” or “the” are used interchangeably with “atleast one,” to mean “one or more” of the element being modified.

As used herein, the terms “over,” “above,” and “under” and the like,with respect to layers in the inkjet media, refer to the order of thelayers over the support, but do not necessarily indicate that the layersare immediately adjacent or that there are no intermediate layers.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features, and advantages of the presentinvention will become more apparent when taken in conjunction with thefollowing description and drawings wherein identical reference numeralshave been used, where possible, to designate identical or analogousfeatures that are common to the figures, and wherein:

FIG. 1 illustrates a cross-sectional view of a typical organic thin filmtransistor having a bottom contact configuration; and

FIG. 2 illustrates a cross-sectional view of a typical organic thin filmtransistor having a top contact configuration.

DESCRIPTION OF THE INVENTION

Cross-sectional views of typical organic thin film transistor are shownin FIGS. 1 and 2, wherein in FIG. 1 illustrates a typical bottom contactconfiguration and FIG. 2 illustrates a typical top contactconfiguration.

Each thin film transistor (TFT) in FIGS. 1 and 2 contains a sourceelectrode 20, a drain electrode 30, a gate electrode 44, a gatedielectric 56, a substrate 28, and the semiconductor 70 of the inventionin the form of a film connecting the source electrode 20 to drainelectrode 30, which semiconductor comprises a compound selected from theclass of N,N′-di(arylalkyl) substituted 3,4,9,10 perylenetetracarboxylic acid diimide compounds described herein.

When the TFT operates in an accumulation mode, the charges injected fromthe source electrode into the semiconductor are mobile and a currentflows from source to drain, mainly in a thin channel region within about100 Angstroms of the semiconductor-dielectric interface. See A.Dodabalapur, L. Torsi H. E. Katz, Science 1995, 268, 270, herebyincorporated by reference. In the configuration of FIG. 1, the chargeneed only be injected laterally from the source electrode 20 to form thechannel. In the absence of a gate field the channel ideally has fewcharge carriers; as a result there is ideally no source-drainconduction.

The off current is defined as the current flowing between the sourceelectrode 20 and the drain electrode 30 when charge has not beenintentionally injected into the channel by the application of a gatevoltage. For an accumulation-mode TFT, this occurs for a gate-sourcevoltage more negative, assuming an n-channel, than a certain voltageknown as the threshold voltage. See Sze in Semiconductor Devices—Physicsand Technology, John Wiley & Sons (1981), pages 438-443. The on currentis defined as the current flowing between the source electrode 20 andthe drain electrode 30 when charge carriers have been accumulatedintentionally in the channel by application of an appropriate voltage tothe gate electrode 44, and the channel is conducting. For an n-channelaccumulation-mode TFT, this occurs at gate-source voltage more positivethan the threshold voltage. It is desirable for this threshold voltageto be zero, or slightly positive, for n-channel operation. Switchingbetween on and off is accomplished by the application and removal of anelectric field from the gate electrode 44 across the gate dielectric 56to the semiconductor-dielectric interface, effectively charging acapacitor.

In accordance with the invention, the organic semiconductor materialsused in the present invention, when used in the form of an n-channelfilm, can exhibit high performance under ambient conditions without theneed for special chemical underlayers.

The improved n-channel semiconductor film of the present invention,comprising the N,N′-di(arylalkyl)3,4,9,10 perylene-based tetracarboxylicacid diimide compounds, preferably N,N′-di(phenylalkyl)3,4,9,10perylene-based tetracarboxylic acid diimide compounds, described herein,is capable of exhibiting a field effect electron mobility greater than0.01 cm²/Vs, preferably greater than 0.2 cm²/Vs. Most advantageously,such mobilities are exhibited in air. In fact, theN,N′-di(arylalkyl)3,4,9,10 perylene-based tetracarboxylic acid diimidecompounds described have exhibited mobilities in the range of 0.01-0.7cm²/Vs which are some of the highest thus far reported for n-channelsemiconductor materials in air.

In addition, the n-channel semiconductor film of the invention iscapable of providing on/off ratios of at least 10⁴, advantageously atleast 10⁵. The on/off ratio is measured as the maximum/minimum of thedrain current as the gate voltage is swept from zero to 80 volts and thedrain-source voltage is held at a constant value of 80 volts, andemploying a silicon dioxide gate dielectric.

Moreover, these properties are attainable after repeated exposure of then-type semiconductor material to air, before film deposition, as well asexposure of the transistor device and/or the channel layer to air afterdeposition.

The n-channel semiconductor materials used in the present inventionoffer advantages over other previously reported n-channel semiconductormaterials in that they do not require rigorous exclusion of oxygen toobtain the desired high mobilities.

Without wishing to be bound by theory, there are several factors thatare believed to contribute to the desirable properties of thefluorine-containing perylene-based tetracarboxylic acid diimidecompounds of the present invention. The solid-state structure of thematerial has the individual molecules packed such that the orbitals ofthe conjugated system, those containing the aromatic ring system and/orthe imide carboxyl groups of adjacent molecules, are able to interact,resulting in high mobility. The direction of this interaction has acomponent parallel to the direction of desired current flow in a deviceusing this material as the active layer. The morphology of the filmsformed by the material is substantially continuous, such that currentflows through the material without unacceptable interruption. Inparticular, the compounds used in the invention contain a conjugatedperylene core structure having fused aromatic rings.

The lowest lying unoccupied molecular orbital of the compound is at anenergy that allows for injection of electrons at useful voltages frommetals with reasonable work functions. This conjugated structuregenerally has a desirable lowest unoccupied molecular orbital (LUMO)energy level of about 3.5 eV to about 4.6 eV with reference to thevacuum energy level. As known in the art, LUMO energy level andreduction potential approximately describe the same characteristics of amaterial. LUMO energy level values are measured with reference to thevacuum energy level, and reduction potential values are measured insolution versus a standard electrode An advantage for deviceapplications is that the LUMO in the crystalline solid, which is theconduction band of the semiconductor, and the electron affinity of thesolid both are measured with reference to the vacuum level. The latterparameters are usually different from the former parameters, which areobtained from solution.

As indicated above, the present invention is directed to an articlecomprising, in a thin film transistor, a thin film of organicsemiconductor material that comprises an N,N′-di(arylalkyl)-substitutedperylene-based tetracarboxylic diimide compound having a substituted orunsubstituted carbocyclic aromatic ring system attached to each imidenitrogen atom through a divalent hydrocarbon group, wherein any optionalsubstituents on the aryl rings comprises at least one electron donatingorganic group, i.e., if one or more substituents are present on one orboth of the two carbocyclic ring systems, such substituents comprise atleast one electron donating group. The two carbocyclic ring systems candiffer, and each carbocyclic ring system can independently havedifferent substitution or no substitution. Preferably, however, eachcarbocyclic ring system is the same, although the substitution on eachring system, if any, may differ. Preferably, if both carbocyclic ringsystems are substituted, then both carbocyclic ring systems comprise atleast one electron donating substituent group.

In one embodiment of the invention, an n-channel semiconductor filmcomprises an N,N′-di(phenylalkyl)-substituted 3,4,9,10 perylene-basedtetracarboxylic acid diimide compound represented by general StructureI:

wherein, X is a —CH₂— divalent group, n=1-3, and R1, R2, R3, R4, R5, R6,R7, R8, R9, and R10 are each independently H or an electron donatingorganic group. Preferably, R1, R2, R3, R4 R5, R6, R7, R8, R9, and R10substituents on the phenyl rings comprise at least one electron donatingsubstituent, more preferably an alkyl, most preferably a methyl group.Preferred organic groups include, for example, CH₃, linear or branchedC2-C4 alkyl, alkylene (a monovalent unsaturated aliphatic hydrocarbon),and alkoxy. Accordingly, none of the R1 to R10 groups is anelectronegative group such as a fluorine, trifluoromethyl or otherfluorine-containing groups.

Preferably, in the above structure, at least one phenyl ring issubstituted with a single substituent (most preferably an alkyl group)that is ortho or meta to the position of the —(CH2)_(n)— group linkingthe phenyl and imide nitrogen. Preferably, alternatively, both phenylrings are substituted with a single substituent (most preferably analkyl group) that is ortho or meta to the position of the —(CH2)_(n)—group linking the phenryl and imide nitrogen.

It is preferred that when n=1 at least two of R1, R2, R3, R4 and R5 areH and at least two of R6, R7, R8, R9, and R10 are H. When n=1, morepreferred structures are those in which at least three of R1, R2, R3, R4and R5 are H and at least three of R6, R7, R8, R9, and RIO are H.Preferably, if the divalent hydrocarbon in Structure I is a —CH₂— group,then at least one phenyl group is substituted with a an electrondonating group.

According to one embodiment, when n=1, preferred structures are those inwhich either all of R1, R2, R3, R4, R5, R6, R8, R9, and R10 are H, andR7 is CH₃; or all of R2, R3, R4, R5, R7, R8, R9, and R10 are H, and bothR1 and R6 are CH₃.

It is preferred that when n=2 at least two of R1, R2, R3, R4 and R5 areH and at least two of R6, R7, R8, R9, and R10 are H. When n=2, morepreferred structures are those in which at least three of R1, R2, R3, R4and R5 are H and at least three of R6, R7, R8, R9, and R10 are H. Whenn=2, still more preferred structures are those in which either all ofR1, R2, R3, R4, R5, R6, R8, R9, and R10 are H, and R7 is CH₃; or all ofR2, R3, R4, R5, R7, R8, R9, and R10 are H, and both R1 and R6 are CH₃.

When n=2, most preferred is that structure in which all of R1, R3, R4,R5, R6, R8, R9, and R10 are H, and both R2 and R7 are CH₃.

In the above Structure 1, a first and second dicarboxylic imide moietyis attached on opposite sides of the perylene nucleus, at the 3,4 and9,10 positions of the perylene nucleus. The perylene nucleus can beoptionally substituted with up to eight independently selected Y groups,wherein m is any integer from 0 to 8.

The Y substituent groups on the perylene nucleus can include, forexample, alkyl groups, alkenyl, alkoxy groups, halogens such as fluorineor chlorine, cyano, aryl, arylalkyl or any other groups that do notaffect the n-type semiconductor properties of the film made from suchcompounds. It is advantageous to avoid substituents that tend tointerfere with close approach of the conjugated cores of the compoundsin a stacked arrangement of the molecules that is conducive tosemiconductor properties. Such substituents include highly branchedgroups, ring structures and groups having more than 12 atoms,particularly where such groups or rings would be oriented to pose asignificant steric barrier to the close approach of the conjugatedcores. In addition, substituent groups should be avoided thatsubstantially lower the solubility and/or volatility of the compoundssuch that the desirable fabrication processes are prevented.

Unless otherwise specifically stated, use of the term “substituted” or“substituent” means any group or atom other than hydrogen. Additionally,when the term “group” is used, it means that when a substituent groupcontains a substitutable hydrogen, it is also intended to encompass notonly the substituent's unsubstituted form, but also its form to theextent it can be further substituted (up to the maximum possible number)with any substituent group or groups so long as the substituent does notdestroy properties necessary for semiconductor utility. If desired, thesubstituents may themselves be further substituted one or more timeswith acceptable substituent groups. For example, an alkyl or alkoxygroup can be substituted with one or more fluorine atoms. When amolecule may have two or more substituents, the substituents may bejoined together to form an aliphatic or unsaturated ring such as a fusedring unless otherwise provided.

Examples of any of the above-mentioned alkyl groups, except as otherwiseindicated, are methyl, ethyl, propyl, isopropyl, butyl, isobutyl,t-butyl, pentyl, hexyl, octyl, 2- ethylhexyl, and congeners. Alkylgroups, preferably having 1 to 6 carbon atoms, more preferably 1 to 4,are intended to include branched or linear groups. Alkenyl groups can bevinyl, 1-propenyl, 1-butenyl, 2-butenyl, and congeners. Aryl groups canbe phenyl, naphthyl, styryl, and congeners. Arylalkyl groups can bebenzyl, phenethyl, and congeners. Useful substituents on any of theforegoing or other groups disclosed include halogen, and alkoxy, and thelike. Preferred Y substituents on the perylene nucleus or core areelectron-withdrawing groups. The substituent groups Y can be an organicor inorganic group at any available position on the perylene nucleus,and m is any integer from zero to eight.

When referring to electron donating groups, this can be indicated orestimated by the Hammett substituent constant (σ_(p), σ_(m)), asdescribed by L. P. Hammett in Physical Organic Chemistry (McGraw-HillBook Co., N.Y., 1940), or by the Taft polar substituent constants(σ_(i)) as defined by R. W. Taft in Steric Effects in Organic Chemistry(Wiley and Sons, N.Y., 1956), and in other standard organic textbooks.This parameter which characterizes the ability of ring-substituents (inthe para position) to affect the electronic nature of a reaction site,were originally quantified by their effect on the pKa of benzoic acid.Subsequent work has extended and refined the original concept and data,but for the purposes of prediction and correlation, standard sets ofσ_(p) are widely available in the chemical literature, as for example inC. Hansch et al., J. Med. Chem., 17, 1207 (1973). Preferably, anelectron donating group has a σ_(p) or σ_(m) of less than zero, morepreferably less than −0.05, most preferably less than −0.1. The σ_(p)value can be used to indicate the electron donating nature of the groupin a structure according to the present invention, as in Structure Iabove even when the group is not a para substituent in Structure I.

Specific illustrative examples of useful N,N′-substituted 3,4,9,10perylene-based tetracarboxylic acid diimide derivatives are shown by theformulae below:

Another aspect of the invention relates to the process for theproduction of semiconductor components and electronic devicesincorporating such components. In one embodiment, a substrate isprovided and a layer of the semiconductor material as described abovecan be applied to the substrate, electrical contacts being made with thelayer. The exact process sequence is determined by the structure of thedesired semiconductor component. Thus, in the production of an organicfield effect transistor, for example, a gate electrode can be firstdeposited on a flexible substrate, for example an organic polymer film,the gate electrode can then be insulated with a dielectric and thensource and drain electrodes and a layer of the n-channel semiconductormaterial can be applied on top. The structure of such a transistor andhence the sequence of its production can be varied in the customarymanner known to a person skilled in the art. Thus, alternatively, a gateelectrode can be deposited first, followed by a gate dielectric, thenthe organic semiconductor can be applied, and finally the contacts forthe source electrode and drain electrode deposited on the semiconductorlayer. A third structure could have the source and drain electrodesdeposited first, then the organic semiconductor, with dielectric andgate electrode deposited on top.

The skilled artisan will recognize other structures can be constructedand/or intermediate surface modifying layers can be interposed betweenthe above-described components of the thin film transistor. In mostembodiments, a field effect transistor comprises an insulating layer, agate electrode, a semiconductor layer comprising an organic material asdescribed herein, a source electrode, and a drain electrode, wherein theinsulating layer, the gate electrode, the semiconductor layer, thesource electrode, and the drain electrode are in any sequence as long asthe gate electrode and the semiconductor layer both contact theinsulating layer, and the source electrode and the drain electrode bothcontact the semiconductor layer.

A support can be used for supporting the OTFT during manufacturing,testing, and/or use. The skilled artisan will appreciate that a supportselected for commercial embodiments may be different from one selectedfor testing or screening various embodiments. In some embodiments, thesupport does not provide any necessary electrical function for the TFT.This type of support is termed a “non-participating support” in thisdocument. Useful materials can include organic or inorganic materials.For example, the support may comprise inorganic glasses, ceramic foils,polymeric materials, filled polymeric materials, coated metallic foils,acrylics, epoxies, polyamides, polycarbonates, polyimides, polyketones,poly(oxy-1,4-phenyleneoxy-1,4-phenylenecarbonyl-1,4-phenylene)(sometimes referred to as poly(ether ether ketone) or PEEK),polynorbomenes, polyphenyleneoxides, poly(ethylenenaphthalenedicarboxylate) (PEN), poly(ethylene terephthalate) (PET),poly(phenylene sulfide) (PPS), and fiber-reinforced plastics (FRP).

A flexible support is used in some embodiments of the present invention.This allows for roll processing, which may be continuous, providingeconomy of scale and economy of manufacturing over flat and/or rigidsupports. The flexible support chosen preferably is capable of wrappingaround the circumference of a cylinder of less than about 50 cmdiameter, more preferably 25 cm diameter, most preferably 10 cmdiameter, without distorting or breaking, using low force as by unaidedhands. The preferred flexible support may be rolled upon itself.

In some embodiments of the invention, the support is optional. Forexample, in a top construction as in FIG. 2, when the gate electrodeand/or gate dielectric provides sufficient support for the intended useof the resultant TFT, the support is not required. In addition, thesupport may be combined with a temporary support. In such an embodiment,a support may be detachably adhered or mechanically affixed to thesupport, such as when the support is desired for a temporary purpose,e.g., manufacturing, transport, testing, and/or storage. For example, aflexible polymeric support may be adhered to a rigid glass support,which support could be removed.

The gate electrode can be any useful conductive material. A variety ofgate materials known in the art, are also suitable, including metals,degenerately doped semiconductors, conducting polymers, and printablematerials such as carbon ink or silver-epoxy. For example, the gateelectrode may comprise doped silicon, or a metal, such as aluminum,chromium, gold, silver, nickel, palladium, platinum, tantalum, andtitanium. Conductive polymers also can be used, for example polyaniline,poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) (PEDOT:PSS). Inaddition, alloys, combinations, and multilayers of these materials maybe useful.

In some embodiments of the invention, the same material can provide thegate electrode function and also provide the support function of thesupport. For example, doped silicon can function as the gate electrodeand support the OTFT.

The gate dielectric is provided on the gate electrode. This gatedielectric electrically insulates the gate electrode from the balance ofthe OTFT device. Thus, the gate dielectric comprises an electricallyinsulating material. The gate dielectric should have a suitabledielectric constant that can vary widely depending on the particulardevice and circumstance of use. For example, although a dielectricconstant from about 2 to 100 or even higher is known for a gatedielectric. Useful materials for the gate dielectric may comprise, forexample, an inorganic electrically insulating material. The gatedielectric may comprise a polymeric material, such aspolyvinylidenedifluoride (PVDF), cyanocelluloses, polyimides, etc.

Specific examples of materials useful for the gate dielectric includestrontiates, tantalates, titanates, zirconates, aluminum oxides, siliconoxides, tantalum oxides, titanium oxides, silicon nitrides, bariumtitanate, barium strontium titanate, barium zirconate titanate, zincselenide, and zinc sulfide. In addition, alloys, combinations, andmultilayers of these examples can be used for the gate dielectric. Ofthese materials, aluminum oxides, silicon oxides, and zinc selenide arepreferred. In addition, polymeric materials such as polyimides, andinsulators that exhibit a high dielectric constant. Such insulators arediscussed in U.S. Pat. No. 5,981,970 hereby incorporated by reference.

The gate dielectric can be provided in the OTFT as a separate layer, orformed on the gate such as by oxidizing the gate material to form thegate dielectric. The dielectric layer may comprise two or more layershaving different dielectric constants.

The source electrode and drain electrode are separated from the gateelectrode by the gate dielectric, while the organic semiconductor layercan be over or under the source electrode and drain electrode. Thesource and drain electrodes can be any useful conductive material.Useful materials include most of those materials described above for thegate electrode, for example, aluminum, barium, calcium, chromium, gold,silver, nickel, palladium, platinum, titanium, polyaniline, PEDOT:PSS,other conducting polymers, alloys thereof, combinations thereof, andmultilayers thereof.

The thin film electrodes (e.g., gate electrode, source electrode, anddrain electrode) can be provided by any useful means such as physicalvapor deposition (e.g., thermal evaporation, sputtering) or ink jetprinting. The patterning of these electrodes can be accomplished byknown methods such as shadow masking, additive photolithography,subtractive photolithography, printing, microcontact printing, andpattern coating.

The organic semiconductor layer can be provided over or under the sourceand drain electrodes, as described above in reference to the thin filmtransistor article. The present invention also provides an integratedcircuit comprising a plurality of OTFTs made by the process describedherein. The n-channel semiconductor material made using the abovefluorine-containing N,N′-substituted 3,4,9,10 perylene-basedtetracarboxylic acid diimide compounds are capable of being formed onany suitable substrate which can comprise the support and anyintermediate layers such as a dielectric or insulator material,including those known in the art.

The entire process of making the thin film transistor or integratedcircuit of the present invention can be carried out below a maximumsupport temperature of about 450° C., preferably below about 250° C.,more preferably below about 150° C., and even more preferably belowabout 100° C., or even at temperatures around room temperature (about25° C. to 70° C.). The temperature selection generally depends on thesupport and processing parameters known in the art, once one is armedwith the knowledge of the present invention contained herein. Thesetemperatures are well below traditional integrated circuit andsemiconductor processing temperatures, which enables the use of any of avariety of relatively inexpensive supports, such as flexible polymericsupports. Thus, the invention enables production of relativelyinexpensive integrated circuits containing organic thin film transistorswith significantly improved performance.

Compounds used in the invention can be readily processed and arethermally stable to such as extent that they can be vaporized. Thecompounds possess significant volatility, so that vapor phasedeposition, where desired, is readily achieved. Such compounds can bedeposited onto substrates by vacuum sublimation or by solventprocessing, including dip coating, drop casting, spin coating, bladecoating.

Deposition by a rapid sublimation method is also possible. One suchmethod is to apply a vacuum of 35 mtorr to a chamber containing asubstrate and a source vessel that holds the compound in powdered form,and heat the vessel over several minutes until the compound sublimesonto the substrate. Generally, the most useful compounds formwell-ordered films, with amorphous films being less useful.

Alternatively, for example, the compounds described above can first bedissolved in a solvent prior to spin-coating or printing for depositionon a substrate.

Devices in which the n-channel semiconductor films of the invention areuseful include especially thin film transistors (TFTs), especiallyorganic field effect thin-film transistors. Also, such films can be usedin various types of devices having organic p-n junctions, such asdescribed on pages 13 to 15 of US 2004,0021204 A1 to Liu, which patentis hereby incorporated by reference.

Electronic devices in which TFTs and other devices are useful include,for example, more complex circuits, e.g., shift registers, integratedcircuits, logic circuits, smart cards, memory devices, radio-frequencyidentification tags, backplanes for active matrix displays,active-matrix displays (e.g. liquid crystal or OLED), solar cells, ringoscillators, and complementary circuits, such as inverter circuits, forexample, in combination with other transistors made using availablep-type organic semiconductor materials such as pentacene. In an activematrix display, a transistor according to the present invention can beused as part of voltage hold circuitry of a pixel of the display. Indevices containing the TFTs of the present invention, such TFTs areoperatively connected by means known in the art.

The present invention further provides a method of making any of theelectronic devices described above. Thus, the present invention isembodied in an article that comprises one or more of the TFTs described.

Advantages of the invention will be demonstrated by the followingexamples, which are intended to be exemplary.

EXAMPLES

A. Material Synthesis

Symmetrical N,N′-dialkyl perylene tetracarboxylic acid diimides used inthis invention are conveniently prepared by cyclizing perylenetetracarboxylic acid dianhydride with excess of suitable amines such asphenylethyl amine. Typical procedures are described in Eur. Pat. Appl.EP 251071 and U.S. Pat. No. 4,156,757 and in U.S. Pat. Nos. 4,578,334and 4,719,163. Typical procedures for preparing unsymmetrical perylenetetracarboxylic acid diimides are described in U.S. Pat. No. 4,714,666.The crude materials were then purified by train sublimation at 10⁻⁵ to10⁻⁶ torr.

B. Device Preparation

In order to test the electrical characteristics of the various materialsof this invention, field-effect transistors were typically made usingthe top-contact geometry. The substrate used is a heavily doped siliconwafer, which also serves as the gate of the transistor. The gatedielectric is a thermally grown SiO2 layer with a thickness of 165 nm.It has been previously shown for both p-type and n-type transistors thatelectrical properties can be improved by treating the surface of thegate dielectric. For most of the experiments described here, the oxidesurface was treated with a thin (<10 nm), spin-coated polymer layer, ora self-assembled monolayer (SAM) of octadecyltrichlorosilane (OTS).Typically, an untreated oxide sample was included in the experiments forcomparison.

The active layer of perylene tetracarboxylic acid diimide was depositedvia vacuum deposition in a thermal evaporator. The deposition rate was0.1 Angstroms per second while the substrate temperature was held at 75°C. for most experiments. The thickness of the active layer was avariable in some experiments, but was typically 40 nm. Silver contactsof thickness 50 nm were deposited through a shadow mask. The channelwidth was held at 500 microns, while the channel lengths were variedbetween 20 and 80 microns. Some experiments were performed to look atthe effect of other contact materials. A few devices were made with abottom-contact geometry, in which the contacts were deposited prior tothe active material.

C. Device Measurement and Analysis Electrical characterization of thefabricated devices was performed with a Hewlett Packard HP 4145b®parameter analyzer. The probe measurement station was held in a positiveN₂ environment for all measurements with the exception of thosepurposely testing the stability of the devices in air. The measurementswere performed under sulfur lighting unless sensitivity to white lightwas being investigated. The devices were exposed to air prior totesting.

For each experiment performed, between 4 and 10 individual devices weretested on each sample prepared, and the results were averaged. For eachdevice, the drain current (Id) was measured as a function ofsource-drain voltage (Vd) for various values of gate voltage (Vg). Formost devices, Vd was swept from 0 V to 80 V for each of the gatevoltages measured, typically 0 V, 20 V, 40 V, 60 V, and 80 V. In thesemeasurements, the gate current (Ig) was also recorded in to detect anyleakage current through the device. Furthermore, for each device thedrain current was measured as a function of gate voltage for variousvalues of source-drain voltage. For most devices, Vg was swept from 0 Vto 80 V for each of the drain voltages measured, typically 40 V, 60 V,and 80 V.

Parameters extracted from the data include field-effect mobility (μ),threshold voltage (Vth), subthreshold slope (S), and the ratio ofIon/Ioff for the measured drain current. The field-effect mobility wasextracted in the saturation region, where Vd>Vg−Vth. In this region, thedrain current is given by the equation (see Sze in SemiconductorDevices-Physics and Technology, John Wiley & Sons (1981)):$I_{d} = {\frac{W}{2L}\mu\quad{C_{ox}\left( {V_{g} - V_{th}} \right)}^{2}}$Where, W and L are the channel width and length, respectively, andC_(ox) is the capacitance of the oxide layer, which is a function ofoxide thickness and dielectric constant of the material. Given thisequation, the saturation field-effect mobility was extracted from astraight-line fit to the linear portion of the √i_(d) versus Vg curve.The threshold voltage, V_(th), is the x-intercept of this straight-linefit. Mobilities can also be extracted from the linear region, whereVd≦Vg−Vth. Here the drain current is given by the equation (see Sze inSemiconductor Devices—Physics and Technology, John Wiley & Sons (1981)):$I_{d} = {\frac{W}{L}\mu\quad{C_{ox}\left\lbrack {{V_{d}\left( {V_{g} - V_{th}} \right)} - \frac{V_{d}^{2}}{2}} \right\rbrack}}$

For these experiments, mobilities in the linear regime were notextracted, since this parameter is very much affected by any injectionproblems at the contacts. In general, non-linearities in the curves ofI_(d) versus V_(d) at low V_(d) indicate that the performance of thedevice is limited by injection of charge by the contacts. In order toobtain results that are more independent of contact imperfections of agiven device, the saturation mobility rather than the linear mobilitywas extracted as the characteristic parameter of device performance.

The log of the drain current as a function of gate voltage was plotted.Parameters extracted from the log I_(d) plot include the I_(on)/I_(off)ratio and the sub-threshold slope (S). The I_(on)/I_(off) ratio issimply the ratio of the maximum to minimum drain current, and S is theinverse of the slope of the I_(d) curve in the region over which thedrain current is increasing (i.e. the device is turning on).

D. Results

The following examples demonstrate that compared to N,N′-diphenyl3,4,9,10 perylene tetracarboxylic acid diimide, inventive devicescomprising arylalkyl-containing N,N′-substituted 3,4,9,10 perylene-basedtetracarboxylic acid diimides provide improved n- channel semiconductorfilms having high mobility and on/off ratio. The mobility calculated inthe saturation region was between 0.04 and 0.7 cm²/Vs, with an on/offratio of 10⁴ to 10⁵. In addition to the improved performance, thedevices also show improved stability in air relative to typicaln-channel TFTs; and excellent reproducibility.

Comparison Example 1

This example demonstrates the n-type TFT device made from anN,N′-diphenyl 3,4,9,10 perylene tetracarboxylic acid diimide C-1

A heavily doped silicon wafer with a thermally-grown SiO₂ layer with athickness of 165 nm was used as the substrate. The wafer was cleaned for10 minutes in a piranah solution, followed by a 6-minute exposure in aUV/ozone chamber. The cleaned surface was then treated with aself-assembled monolayer of octadecyltrichlorosilane (OTS), made from aheptane solution under a humidity-controlled environment. Water contactangles and layer thicknesses were measured to ensure the quality of thetreated surface. Surfaces with a good quality OTS layer have watercontact angles >90°, and thicknesses determined from ellipsometry in therange of 27 Å to 35 Å.

The purified N,N′-diphenyl-3,4,9,10 perylene tetracarboxylic aciddiimide C-1 was deposited by vacuum sublimation at a pressure of 5×10⁻⁷Torr and a rate of 0.1 Angstroms per second to a thickness of 40 nm asmeasured by a quartz crystal. During deposition the substrate was heldat a constant temperature of 75° C. The sample was exposed to air for ashort time prior to subsequent deposition of Ag source and drainelectrodes through a shadow mask to a thickness of 50 nm. The devicesmade had a 500 micron channel width, with channel lengths varying from20-80 microns. Multiple OTFTs were prepared and representative samplesof 4-10 OTFTs were tested for each deposition run. The averaged resultsappear in Table 1 below.

The devices were exposed to air prior to measurement in a nitrogenatmosphere using a Hewlett-Packard 4145B® semiconductor parameteranalyzer. For a typical transistor, with W/L=515/85, the field effectmobility, μ, was calculated from the slope of the (I_(D))^(1/2) versusV_(G) plot to be 2.2×10⁻³ cm²/Vs in the saturation region. The on/offratio was 5.1×10³ and the threshold voltage V_(T)=50 V. Saturationmobilities of up to 2.8×10⁻³ cm²/Vs were measured from similar devicesprepared in this way.

Example 2

This example demonstrates the improved performance of an n-type TFTdevice using N,N′-(2-methylphenyl)methyl-3,4,9,10 perylenetetracarboxylic acid diimide 1-9 in accordance with the presentinvention.

An n-type TFT device using compound I-9 as the active material was madeas in Example 1. Accordingly, compound I-9 was deposited by vacuumsublimation at a pressure of 5×10⁻⁷ Torr and a rate of 0.1 Angstroms persecond to a thickness of 40 nm as measured by a quartz crystal. Duringdeposition the substrate was held at a constant temperature of 75° C.The sample was exposed to air for a short time prior to subsequentdeposition of Ag source and drain electrodes through a shadow mask to athickness of 50 nm. The devices made had an approximately 500 micronchannel width, with channel lengths varying from 20-80 microns. Multipleorganic thin film transistors (OTFTs) were prepared and representativesample of 4 to 10 OTFTs were tested for each deposition run. Theaveraged results appear in Table I below.

The devices were exposed to air prior to measurement in a nitrogenatmosphere using a Hewlett-Packard 4145B® semiconductor parameteranalyzer. The field effect mobility, μ, was calculated from the slope ofthe (I_(D))^(1/2) versus V_(G) plot to be 0.11 cm²/Vs in the saturationregion. The on/off ratio was 4.4×10⁴ and the threshold voltageV_(T)=42.4 V. Saturation mobilities of up to 0.15 cm²/Vs were measuredfrom similar devices prepared in this way. TABLE 1 Active OTFT μ V_(th)σ Material (cm²/Vs) σ (μ) (V) (V_(th)) I_(on)/I_(off) Com- C-1 2.2 ×10⁻³ 6.48 × 10⁻⁴ 52.74 5.51 5.1 × 10³ parison Example 1 Inventive I-90.10  6.8 × 10⁻² 42.4 1.2 4.5 × 10⁴ Example 2

This example clearly demonstrates the advantage of using compound I-9 asn-type material. Thus, both the mobility and the on/off ratio areimproved over Comparison Example 1, clearly demonstrating the effect of—CH₂— groups between diimide nitrogen and phenyl ring on deviceperformance.

Example 3

This example demonstrates the improved performance n-type TFT devicemade from N,N′-diphenylethyl-substituted 3,4,9,10 perylene-basedtetracarboxylic acid diimide I-1 in accordance with the presentinvention.

An n-type TFT device using compound I-1 as the active material was madeas in Example 1. Accordingly, compound I-1 was deposited by vacuumsublimation at a pressure of 5×10⁻⁷ Torr and a rate of 0.1 Angstroms persecond to a thickness of 40 nm as measured by a quartz crystal. Duringdeposition the substrate was held at a constant temperature of 75° C.The sample was exposed to air for a short time prior to subsequentdeposition of Ag source and drain electrodes through a shadow mask to athickness of 50 nm. The devices made had an approximately 500 micronchannel width, with channel lengths varying from 20-80 microns. Multipleorganic thin film transistors (OTFTS) were prepared and representativesample of 4 to 10 OTFTs were tested for each deposition run. Theaveraged results appear in Table 1 below.

The devices were exposed to air prior to measurement in a nitrogenatmosphere using a Hewlett-Packard 4145B® semiconductor parameteranalyzer. For a device having a channel length of 39 microns and achannel width of 520 microns, the field effect mobility, μ, wascalculated from the slope of the (I_(D))^(1/2) versus V_(G) plot to be0.042 cm²/Vs in the saturation region. The on/off ratio was 1×10⁵ andthe threshold voltage V_(T)=38.4 V. Saturation mobilities of up to 0.07cm²/Vs were measured from similar devices prepared in this way. TABLE 2Active OTFT μ V_(th) σ Material (cm²/Vs) σ (μ) (V) (V_(th))I_(on)/I_(off) Com- C-1 2.2 × 10⁻³ 6.48 × 10⁻⁴ 52.74 5.51 5.1 × 10³parative Example 1 Inventive I-1 4.2 × 10⁻² 1.20 × 10⁻² 38.4 6.0 1.0 ×10⁵ Example 3

This example clearly demonstrates the advantage of compound I-1 asn-type material. Thus, both the mobility and the on/off ratio areimproved over Comparative Example 1, clearly demonstrating the effect of—CH₂—CH₂— groups between diimide nitrogen and phenyl ring on deviceperformance.

Example 4

This example demonstrates the improved performance n-type TFT devicemade from a fluorine-containing N,N′-di(2-methylphenyl)ethyl-3,4,9,10perylene tetracarboxylicacid diimide I-2. An n-type TFT device usingcompound I-2 as the active material of the OTFT was made as inExample 1. Multiple OTFTs were prepared and tested for each depositionrun. The averaged results appear in Table 3. TABLE 3 Active OTFT μV_(th) σ Material (cm²/Vs) σ (μ) (V) (V_(th)) I_(on)/I_(off) ComparisonC-1 2.2 × 10⁻³ 6.5 × 10⁻⁴ 52.74 5.51 5.1 × 10³ Example 1 Inventive I-20.24 4.6 × 10⁻² 46.8 2.4 6.5 × 10⁵ Example 4

This example clearly demonstrates the advantage of compound I-2 asn-type material. From the slope of the (I_(D))^(1/2) versus V_(G) plotsaturation region mobilities of up to 0.3 cm²/Vs were measured fromsimilar devices prepared in this way.

Thus, both the mobility and the on/off ratio are improved by orders ofmagnitude over Comparative Example 1, clearly demonstrating the effectof (2-methylphenyl)ethyl groups on diimide nitrogens on the deviceperformance.

Example 5

This example demonstrates the improved performance of an n-type TFTdevice made from a fluorine-containingN,N′-di(3-methylphenyl)ethyl-3,4,9,10 perylenetetracarboxylic aciddiimide I-3. An n-type TFT device using compound 1-3 as the activematerial of the OTFT was made as in Example 1. Multiple OTFTs wereprepared and tested for each deposition run. The averaged results appearin Table 4. TABLE 4 Active OTFT μ V_(th) σ Material (cm²/Vs) σ (μ) (V)(V_(th)) I_(on)/I_(off) Comparison C-1 2.2 × 10⁻³ 6.5 × 10⁻⁴ 52.7 5.55.1 × 10³ Example 1 Inventive I-3 0.7 2.3 × 10⁻¹ 45.2 5.7 1.4 × 10⁶Example 5

This example clearly demonstrates the advantage of compound I-3 asn-type material. From the slope of the (I_(D))^(1/2) versus V_(G) plotsaturation region mobilities of up to 0.9 cm²/Vs were measured fromsimilar devices prepared in this way. Thus, both the mobility and theon/off ratio are improved by orders of magnitude over ComparativeExample 1, clearly demonstrating the effect on the device performance,of the ethyl(3-methylphenyl) groups on the diimide nitrogens in compoundI-3.

Example 6

This example demonstrates the robustness of the active materials used inthe present invention with respect to the substrate temperature duringdeposition of semiconductor material.

Samples were prepared as in Inventive Example 4, except that thesubstrate temperature during deposition of semiconductor material I-3was varied from 50° C. to 75° C. The results are summarized in Table 5,demonstrating the robustness to substrate temperature duringsemiconductor layer deposition and the improved electrical performanceof compound I-3 material. TABLE 5 Active Temperature OTFT μ V_(th) σ (°C.) Material (cm²/Vs) σ (μ) (V) (V_(th)) I_(on)/I_(off) 50 I-3 0.64 2.8× 10⁻¹ 43.3 6.5 4.7 × 10⁵ 75 I-3 0.67 2.3 × 10⁻¹ 45.2 5.7 1.4 × 10⁶

Example 7

This example (Table 6) demonstrates the robustness with respect to thedevice stability over a 3 week period of the active material made usingcompound I-3 in accordance with the present invention. TABLE 6 TimeActive Elapsed OTFT μ (days) Material (cm²/Vs) σ (μ) V_(th) (V) σ(V_(th)) I_(on)/I_(off) 1 I-3 0.53 2.8 × 10⁻⁴ 32.6 6.5 1.7 × 10⁶ 21 I-30.56 2.3 × 10⁻⁴ 37 5.7 5.0 × 10⁵Parts List:

-   20 source electrode-   28 substrate-   30 drain electrode-   44 gate electrode-   56 gate dielectric-   70 semiconductor

1. An article comprising, in a thin film transistor, a thin film oforganic semiconductor material that comprises anN,N′-di(arylalkyl)-substituted perylene-based tetracarboxylic diimidecompound having a substituted or unsubstituted carbocyclic aromatic ringsystem attached to each imide nitrogen atom through a divalenthydrocarbon group, wherein substituents, if any, on each carbocyclicaromatic ring system comprise at least one electron donating organicsubstituent.
 2. The article of claim 1 wherein the thin film transistoris a field effect transistor comprising a dielectric layer, a gateelectrode, a source electrode and a drain electrode, and wherein thedielectric layer, the gate electrode, the thin film of organicsemiconductor material, the source electrode, and the drain electrodeare in any sequence as long as the gate electrode and the film oforganic semiconductor material both contact the dielectric layer, andthe source electrode and the drain electrode both contact the thin filmof the organic semiconductor material.
 3. The article of claim 1 whereinthe thin film of organic semiconducting material is capable ofexhibiting electron mobility greater than 0.01 cm²/Vs.
 4. The article ofclaim 1, wherein the thin film of organic semiconductor materialcomprises a N,N′-di(arylalkyl)-substituted 3,4,9,10 perylene-basedtetracarboxylic acid diimide compound represented by the followingstructure:

wherein, X is a —CH₂— divalent group, n=1-3, and R1, R2, R3, R4, R5, R6,R7, R8, R9, and R10, on a first and second phenyl ring in the structure,are each independently H or an electron donating organic group.
 5. Thearticle of claim 4 wherein either one or both of the first and secondphenyl rings, in said structure, are substituted with at least oneelectron donating group.
 6. The article of claim 5 wherein the at leastone electron donating group is an alkyl group.
 7. The article of claim1, wherein in said structure R1, R2, R3, R4, R5, R6, R7, R8, R9, and R10are each independently selected from H, CH₃, linear or branched C₂-C₄alkyl, alkenyl, alkoxy, or other electron donating organic group having1 to 4 carbon atoms.
 8. The article of claim 1, wherein in saidstructure n=1 or 2 and at least two of R1, R2, R3, R4 and R5 are H andat least two of R6, R7, R8, R9, and R10 are H.
 9. The article of claim1, wherein in said structure n=1 or 2 and at least three of R1, R2, R3,R4 and R5 are H and at least three of R6, R7, R8, R9,and R10 are H. 10.The article of claim 1, wherein in said structure n=1 or 2 and eitherall of R1, R2, R3, R4, R5, R6, R8, R9, and R10 are H, and R7 is CH₃; orall of R2, R3, R4, R5, R7, R8, R9, and R10 are H, and both R1 and R6 areCH₃.
 11. The article of claim 1, wherein in said structure n=2 and allof R1, R3, R4, R5, R6, R8, R9, and R10 are H, and both R2 and R7 areCH₃.
 12. The article of claim 1, wherein in said structure at least onephenyl ring is substituted with a single substituent that is ortho ormeta to the position of the —(CH2)_(n)— group linking the phenyl andimide nitrogen.
 13. The article of claim 1, wherein in said structureboth phenyl rings are substituted with a single substituent that isortho or meta to the position of the —(CH2)_(n)— group linking thephenyl and imide nitrogen.
 14. The article of claim 4 wherein Y isindependently selected from alkyl, alkenyl, and alkoxy groups.
 15. Thearticle of claim 1, wherein the thin film transistor has an on/off ratioof a source/drain current of at least 10⁴.
 16. The article of claim 2,wherein the gate electrode is adapted for controlling, by means of avoltage applied to the gate electrode, a current between the source anddrain electrodes through the thin film of organic semiconductormaterial.
 17. The article of claim 16 wherein the gate dielectriccomprises an inorganic or organic electrically insulating material. 18.The article of claim 1 wherein the thin film transistor furthercomprises a non-participating support that is optionally flexible. 19.The article of claim 2 wherein the source, drain, and gate electrodeseach independently comprise a material selected from doped silicon,metal, and a conducting polymer.
 20. An electronic device selected fromthe group consisting of integrated circuits, active-matrix display, andsolar cells comprising a multiplicity of thin film transistors accordingto claim
 1. 21. The electronic device of claim 20 wherein themultiplicity of the thin film transistors is on a non-participatingsupport that is optionally flexible.
 22. A process for fabricating athin film semiconductor device, comprising, not necessarily in thefollowing order, the steps of: (a) depositing, onto a substrate, a thinfilm of n-channel organic semiconductor material that comprises anN,N′-di(arylalkyl)-substituted perylene-based tetracarboxylic diimidecompound having a substituted or unsubstituted carbocyclic aromatic ringsystem attached to each imide nitrogen atom through a divalenthydrocarbon group, wherein substituents, if any, on each carbocyclicaromatic ring system comprise at least one electron donating organicgroup, such that the organic semiconductor material exhibits a fieldeffect electron mobility that is greater than 0.01 cm²/Vs; (b) forming aspaced apart source electrode and drain electrode, wherein the sourceelectrode and the drain electrode are separated by, and electricallyconnected with, the n-channel semiconductor film; and. (c) forming agate electrode spaced apart from the organic semiconductor material. 23.The process of claim 22, wherein said compound is deposited on thesubstrate by sublimation or by solution-phase deposition and wherein thesubstrate has a temperature of no more than 100° C. during deposition.24. The process of claim 22 wherein there is no prior treatment ofinterfaces between the electrodes and the thin film of n-channel organicsemiconductor material.
 25. The process of claim 22 wherein the compoundis N,N′-bis[2-methyl-phenylethyl]-perylene 3,4,9,10 tetracarboxylic aciddiimide, N,N′-bis[3-methyl-phenylethyl]-perylene 3,4,9,10tetracarboxylic acid diimide, orN,N′-bis[2-methyl-phenylmethyl]-perylene 3,4,9,10 tetracarboxylic aciddiimide or N,N′-bis[3-methyl-phenylmethyl]-perylene 3,4,9,10tetracarboxylic acid diimide or N-(2-methyl-phenylethyl),N′-(phenylethyl)-perylene 3,4,9,10 tetracarboxylic acid diimide.
 26. Theprocess of claim 22 comprising, not necessarily in order, the followingsteps: (a) providing a substrate; (b) providing a gate electrodematerial over the substrate (c) providing a gate dielectric over thegate electrode material; (d) depositing the thin film of n-channelorganic semiconductor material over the gate dielectric: (e) providing asource electrode and a drain electrode contiguous to the thin film ofn-channel organic semiconductor material.
 27. The process of claim 26wherein the steps are performed in the order listed.
 28. The process ofclaim 26 wherein the substrate is flexible.
 29. The process of claim 26carried out in its entirety below a peak temperature of 100° C.
 30. Anintegrated circuit comprising a plurality of thin film transistors madeby the process of claim 22.